Engine shuts off intermittently while driving

1969 CHEVROLET NOVA
15,000 MILES • 5.7L • V8 • 2WD • MANUAL
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ESB69NOVA
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A 350 SBC. Aftermarket HEI. Car runs great, but suddenly only for about 5 minutes. Does not overheat. The car does not seem starved for fuel. No leaks. It will shut off completely (not what I would call stalling) and will not restart while coasting in neutral. It starts right up if I switch the ignition completely off and back on again but will not start from any other key position. It will drive about 500 feet and the problem begins all over again with the same results. I'm thinking neutral safety switch but haven't yet found any evidence. Thank you in advance for your advice!
Apr 16, 2022 at 1:32 PM
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JACOBANDNICKOLAS
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Hi,

The neutral safety switch will prevent it from cranking if it isn't in park or neutral, but it won't cause the stall.

To me, it sounds ignition related. If you allow the engine to idle, does it stay running? If not, do me a favor. Check to see if the coil power supply is losing power when this happens. I have no schematics to look at because of the ignition change, but at the distributor, there should be a power supply for the ignition coil that is hot with the key on and in the start position. If you find there is a power loss, I would next check the ignition switch for wiring issues.

Let me know what you find.

Take care,

Joe
Apr 16, 2022 at 8:41 PM
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ESB69NOVA
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Joe,

I let the car middle for 30 minutes. No problem. As soon as I drive it, it shuts off repeatedly every 3-5 minutes.
Thanks,
Ed
Apr 16, 2022 at 9:37 PM
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JACOBANDNICKOLAS
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Ed,

I suspect it is ignition-related, but the idea that it idles makes it a bit more difficult. If it was fuel-related, it would take cranking for some time to refill the carb bowl and not start immediately.

Do me a favor. When it is running (idle) wiggle the wiring harness to the distributor. If there is no change, do the same with the wiring to the switch.

Let me know if anything changes.

Joe
Apr 16, 2022 at 10:37 PM
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ESB69NOVA
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Joe,

I let it idle for about 20 minutes. Warmed it to 190F. Wiggled the wiring harness and every other wire. Then drove it, it quit running.
Ed
Apr 17, 2022 at 4:22 PM
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JACOBANDNICKOLAS
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Ed,

I am going to ask another tech that is better than me on the older vehicles. Let's see what he says. Hang in there.

Also, let me know if you checked the ignition control module.

Joe
Apr 17, 2022 at 8:03 PM
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JACOBANDNICKOLAS
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Hi,

I wanted to let you know I got a reply from the site owner. I asked about your problem. Here is his reply to me:

"I have seen the fuel lines at the tank do this, even if they don't leak, they can allow air to enter the suction side of the pump which will stop the pump operation"

It may be worth checking to see if they are in good condition.

Let me know.

Joe
Apr 18, 2022 at 7:45 PM
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ESB69NOVA
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Thanks! I'll try that next. It'll be a few days. I need to attend to a family health issue.
Apr 18, 2022 at 11:22 PM
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JACOBANDNICKOLAS
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Hi,

You are very welcome. I hope everything is okay at home. Take your time and let me know when you get a chance.

Take care,

Joe
Apr 19, 2022 at 4:39 PM